In recent years, with the extensive application of a variety of portable electronic products, lithium-ion rechargeable battery, due to its superior characteristics such as high voltage, high capacity, low voltage loss, and zero-memory-effect, has been widely used in a variety of applications. However, if short-circuiting occurs within the battery, the internal current rises, the internal pressure rises, and the battery may explode or ignite and burn.
Chinese patent, Number 96197204.1, discloses a type of battery that uses a PTC component. In normal charge state, the resistance of the PTC component is comparatively small. In short-circuit state, the current through the component is large and the temperature rises sharply within a short period of time. When the temperature reaches to a certain degree, the resistance of the PTC component goes up suddenly, and the circuit approaches a short-circuit state. When the temperature falls, the PTC component returns to its low-resistance state, and the circuit conducts once again. By using the PTC component, the battery circuit may break during the short-circuit state, and survive such short-circuit state many times.
Chinese patent, Number 98801710.5, discloses an explosion-proof rechargeable battery that uses non-aqueous electrolyte. The internal circuit of the battery can be safely and reliably switch-off when the battery reaches an over-charged state, and the battery uses a circuit-breaker for high temperature state. The structure of the battery is to provide at the seal electrically and mechanically connected upper and lower plates (1, 2). When the internal pressure of the battery exceeds the regulating state, the mechanical connection of the plates (1, 2) breaks and thereby cuts off the electrical connection. Furthermore, the mechanical breaking pressure of the plates decreases in accordance with the increase in the battery volume ratio.
Chinese patent, Number 99121937.6, discloses a safety device for rechargeable batteries. Its characteristic is that at the top opening of the battery case which contains the electrodes and fluid electrolytes there is a sealed gasket below which are electrode plates that are stacked from the bottom to the top. Between the electrode plate and the top cover is a circuit-cutoff component. This circuit-cutoff component breaks when the electrode plates expand and exert pressure on the circuit-cutoff component, and the circuit-cutoff component breaks and cut off the circuit, ensuring the battery against the abnormal activity or explosion.
Chinese patent, Number 01252383.6, discloses a type of explosion-proof lithium-ion battery, providing on the cover of the battery an explosion-proof safety valve. When the battery short-circuits, the internal energy rapidly releases and the internal pressure increases. When the internal pressure reaches the limit of the explosion-proof safety valve, the valve opens to release the buildup of the high pressure gases and reduces the pressure in the battery, thereby preventing the battery from exploding.
Although the above-mentioned public and patented technologies may improve battery safety performance to a certain extent, there exist certain disadvantages as well. Generally speaking, the structure is complex, the cost is high, and the battery or battery packs occupy large amount of space, affecting overall battery capacity. Furthermore, when the battery short-circuits, although safety measures are taken, the short-circuited battery is damaged in the process and cannot be used again.
Moreover, in the above-mentioned public and patented technologies, the electrode group usually is consist of the positive electrode plates, the insulator, the negative electrode plates, all stacked and wound to form the electrode core. The core may be manufactured in cylindrical or square shapes to form the lithium-ion rechargeable battery, typically of low capacity. However, for battery-driven electric vehicles, battery-driven electric bicycles, communication switches, aerospace and aircraft power sources and large-capacity units for industrial and household applications, these power sources normally consist of several high capacity batteries connected in series to form battery groups. For these types of high capacity batteries, a high level of safety performance is required. If a winding structure is used, the length of the electrode plate may reach over ten meters or multiples thereof and the winding becomes extremely difficult. Moreover, this structure has a rather small heat dissipation area, not conducive for internal heat dissipation, affecting the high discharge rate of the battery. Therefore, for large current and large discharge applications, the winding structure is not suitable.
When compared with other types of rechargeable battery, lithium-ion battery has high internal resistance. When the battery is in a high discharge state, the voltage falls sharply, the discharge time shortens considerably, and the battery capacity is greatly reduced. The low conduction characteristic of the normal electrode is one of the primary reasons why lithium-ion battery has high internal resistance. At present, most commercial lithium-ion batteries use one or more conducting tabs (also called current collector) as the conductor for current flow. But such current flow is limited to a few welding-spots, resulting in low conductibility and uneven current flow in the charge/discharge process. Thus, such conducting tabs are not suitable for batteries wanting high capacity, high discharge, and high performing recharge cycle characteristics.
More importantly, in the design of high capacity batteries, such as for use as motor-power batteries, its safety performance is a primary factor to consider. For common lithium-ion rechargeable batteries, the conducting tabs are welded to the positive and negative electrode covers. When the battery is dropped or severely shaken, the core can easily move, causing the positive and the negative plates to move from its positions and the internal circuit to break. At the same time, the force bearing parts typically are at the welding spots of the conducting tabs, which can easily cause the welding-spots to fall off, thereby causing a series of safety problems.
Given the concerns over prior art battery designs, it is therefore desirable to provide novel designs avoiding prior art issues.